Here after a study to investigate the role of lower joints onto vertical jump

RELATIVE CONTRIBUTION OF LOWER EXTHREMITY JOINT KINETICS TO VERTICAL
JUMPING PERFORMANCE

NSCA Abstracts (Loren Chiu)

Vertical jump (VJ) performance is recognized as an important measure
of explosive strength and is related to sport performance including,
weightlifting, sprinting and cycling. A number of investigations have
attempted to determine the relative contribution of the ankle plantar-
flexors, and knee and hip extensors to VJ performance.

These investigations have generally utilized descriptive statistics
of joint kinetics, however, no investigations have determined the
relationship between joint kinetics and VJ performance. PURPOSE: To
determine the relative contribution of joint kinetics to VJ
performance utilizing regression analysis.

METHODS: 13 men, competing in power sports (weightlifting, track &
field, volleyball) performed restricted (no arm swing) VJ on a force
platform. Lower extremity kinematics were recorded from a 6-degree of
freedom passive reflective marker set by 8 optoelectric cameras.
Standard 3D inverse dynamics were applied to determine the net joint
moment (peak), impulse, power (peak concentric & eccentric) and work
(concentric, eccentric & total) at the ankle, knee and hip joints.
Data for left and right limbs were summed and normalized to body
mass. Correlations were determined between the kinetic variables and
VJ height.

RESULTS: Significant correlations existed between VJ height with: 1)
concentric net joint power (ankle, knee & hip), 2) concentric net
joint work (ankle, knee & hip), and 3) total net joint work (knee &
hip). Stepwise linear regression models were generated for each data
subset. The regression model utilizing total net joint work resulted
in the greatest explained variance (R² =0.63; p=0.007). Hip
work generated an R² =0.39 (p=0.023) & addition of knee
work resulted in an R² change = 0.24 (p=0.029).
Standardized Beta-coefficients were 0.341 (hip work) and 0.566 (knee
work). Tolerance (0.752) and VIF (1.329) statistics indicate that
multicollinearity was low.

DISCUSSION: The regression model generated indicates that total net
joint work performed by the hip and knee extensors explains 63% of
the variability in VJ performance. As the VJ is a time-dependent
task, greater work can be generated if rate of force development
increases. The standardized Beta-coefficients suggest that increasing
knee extensor work has a greater effect on vertical jump performance
than increasing hip extensor work.

Exercises that require large rate of force development at the knee
extensors, primarily, and hip extensors, secondarily, may therefore
be most effective for improving vertical jump performance. The role
of the ankle plantar-flexors should not be dismissed, however, as the
small sample size resulted in a non-significant correlation (r=0.42;
p=0.16) between total ankle work and VJ height. A larger
investigation may elucidate the contribution of the ankle plantar-
flexors to the current regression model. This investigation was
supported by an NSCA Student Research Grant.

--------------------------------------------

It seems that the leg extention could be the better exercise to do.
What's your comments?